2、工廠模式

工廠模式分爲：簡單工廠，工廠方法，抽象工廠。簡單工廠隨簡單但是用得最多，抽象工廠雖然更抽象更系統，但是用的很少。工廠模式總的來說就是爲了解決實例化多個不同子類的情況，其實是爲了方便調用者實例化子類過多的情況，在你通往架構師的道路上，你要有一種感覺，new對象是一種硬編碼，儘量不要自己new，要將這個操作讓別人或者專門的人來做。

1、簡單工廠demo

public interface Shape {
   void draw();
}

public class Rectangle implements Shape {
 
   @Override
   public void draw() {
      System.out.println("Inside Rectangle::draw() method.");
   }
}

public class Square implements Shape {
 
   @Override
   public void draw() {
      System.out.println("Inside Square::draw() method.");
   }
}

public class Circle implements Shape {
 
   @Override
   public void draw() {
      System.out.println("Inside Circle::draw() method.");
   }
}

public class ShapeFactory {
    
   // 使用 getShape 方法獲取形狀類型的對象
   public Shape getShape(String shapeType){
      if(shapeType == null){
         return null;
      }
      if(shapeType.equalsIgnoreCase("CIRCLE")){
         return new Circle();
      } else if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new Rectangle();
      } else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new Square();
      }
      return null;
   }
}

簡單工廠在shiro中使用，實際使用總是看起來難以理解一點，正如現實和理想一樣，這裏輸出的實例有兩種類型WebDelegatingSubject和DelegatingSubject兩種類型，抓住這個特點看看。

package org.apache.shiro.web.mgt;

import org.apache.shiro.mgt.DefaultSubjectFactory;
import org.apache.shiro.mgt.SecurityManager;
import org.apache.shiro.session.Session;
import org.apache.shiro.subject.PrincipalCollection;
import org.apache.shiro.subject.Subject;
import org.apache.shiro.subject.SubjectContext;
import org.apache.shiro.web.subject.WebSubjectContext;
import org.apache.shiro.web.subject.support.WebDelegatingSubject;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import org.apache.shiro.web.subject.WebSubject;

public class DefaultWebSubjectFactory extends DefaultSubjectFactory {

    public DefaultWebSubjectFactory() {
        super();
    }

    public Subject createSubject(SubjectContext context) {
        //SHIRO-646
        //Check if the existing subject is NOT a WebSubject. If it isn't, then call super.createSubject instead.
        //Creating a WebSubject from a non-web Subject will cause the ServletRequest and ServletResponse to be null, which wil fail when creating a session.
        boolean isNotBasedOnWebSubject = context.getSubject() != null && !(context.getSubject() instanceof WebSubject);
        if (!(context instanceof WebSubjectContext) || isNotBasedOnWebSubject) {
            return super.createSubject(context);
        }
        WebSubjectContext wsc = (WebSubjectContext) context;
        SecurityManager securityManager = wsc.resolveSecurityManager();
        Session session = wsc.resolveSession();
        boolean sessionEnabled = wsc.isSessionCreationEnabled();
        PrincipalCollection principals = wsc.resolvePrincipals();
        boolean authenticated = wsc.resolveAuthenticated();
        String host = wsc.resolveHost();
        ServletRequest request = wsc.resolveServletRequest();
        ServletResponse response = wsc.resolveServletResponse();

        return new WebDelegatingSubject(principals, authenticated, host, session, sessionEnabled,
                request, response, securityManager);
    }

}

3、抽象工廠

public interface Shape {
   void draw();
}


public class Rectangle implements Shape {
 
   @Override
   public void draw() {
      System.out.println("Inside Rectangle::draw() method.");
   }
}

public class Square implements Shape {
 
   @Override
   public void draw() {
      System.out.println("Inside Square::draw() method.");
   }
}

public class Circle implements Shape {
 
   @Override
   public void draw() {
      System.out.println("Inside Circle::draw() method.");
   }
}

public interface Color {
   void fill();
}

public class Red implements Color {
 
   @Override
   public void fill() {
      System.out.println("Inside Red::fill() method.");
   }
}

public class Green implements Color {
 
   @Override
   public void fill() {
      System.out.println("Inside Green::fill() method.");
   }
}

public class Blue implements Color {
 
   @Override
   public void fill() {
      System.out.println("Inside Blue::fill() method.");
   }
}

public abstract class AbstractFactory {
   public abstract Color getColor(String color);
   public abstract Shape getShape(String shape) ;
}

public class ShapeFactory extends AbstractFactory {
    
   @Override
   public Shape getShape(String shapeType){
      if(shapeType == null){
         return null;
      }        
      if(shapeType.equalsIgnoreCase("CIRCLE")){
         return new Circle();
      } else if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new Rectangle();
      } else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new Square();
      }
      return null;
   }
   
   @Override
   public Color getColor(String color) {
      return null;
   }
}


public class ColorFactory extends AbstractFactory {
    
   @Override
   public Shape getShape(String shapeType){
      return null;
   }
   
   @Override
   public Color getColor(String color) {
      if(color == null){
         return null;
      }        
      if(color.equalsIgnoreCase("RED")){
         return new Red();
      } else if(color.equalsIgnoreCase("GREEN")){
         return new Green();
      } else if(color.equalsIgnoreCase("BLUE")){
         return new Blue();
      }
      return null;
   }
}

public class FactoryProducer {
   public static AbstractFactory getFactory(String choice){
      if(choice.equalsIgnoreCase("SHAPE")){
         return new ShapeFactory();
      } else if(choice.equalsIgnoreCase("COLOR")){
         return new ColorFactory();
      }
      return null;
   }
}

public class AbstractFactoryPatternDemo {
   public static void main(String[] args) {
 
      //獲取形狀工廠
      AbstractFactory shapeFactory = FactoryProducer.getFactory("SHAPE");
 
      //獲取形狀爲 Circle 的對象
      Shape shape1 = shapeFactory.getShape("CIRCLE");
 
      //調用 Circle 的 draw 方法
      shape1.draw();
 
      //獲取形狀爲 Rectangle 的對象
      Shape shape2 = shapeFactory.getShape("RECTANGLE");
 
      //調用 Rectangle 的 draw 方法
      shape2.draw();
      
      //獲取形狀爲 Square 的對象
      Shape shape3 = shapeFactory.getShape("SQUARE");
 
      //調用 Square 的 draw 方法
      shape3.draw();
 
      //獲取顏色工廠
      AbstractFactory colorFactory = FactoryProducer.getFactory("COLOR");
 
      //獲取顏色爲 Red 的對象
      Color color1 = colorFactory.getColor("RED");
 
      //調用 Red 的 fill 方法
      color1.fill();
 
      //獲取顏色爲 Green 的對象
      Color color2 = colorFactory.getColor("Green");
 
      //調用 Green 的 fill 方法
      color2.fill();
 
      //獲取顏色爲 Blue 的對象
      Color color3 = colorFactory.getColor("BLUE");
 
      //調用 Blue 的 fill 方法
      color3.fill();
   }
}